Process for the purification of sodium metaphosphate



5 m teor forming an {art NfiHiPOi. me nar'ilyir as 1 However, suffi Hydra-nae is not added iron and aluminum as orthdphcisphate, Nail-l1 phosphate, naeroi, weui iii solution so as to interfere with obtaining all precipitated communes, wet as the calcium sulphate, are then filtered'o'ff and resulting" solution, containing the sodium diness and fused cooling, the mix some polymeric form thereof, 1 resulting sodium metaphosphat tains a considerable quantity of form of metaphosphates of iron, aluminum, chromium, vanadium, etc., which have a deleterious effect in the various technical uses of the product, as, for instance, when used for the softening of boilers and as a detergent dry work, for washing feed water in steam or water softener in laun or cleansing, in bleaching, in preventing soap cloth, for scouring wool, for kier boiling or increasing the penetration of dyes,

a1 materials and for clean- These impurities, and particularly ds, further cause a discoloraduct. It is the object of spots on cotton, f for cleansing structur ing ceramics. the iron compoun tion ofthe finished pro my invention to While my invention is capable of being carried out in many different ways, for the purpose of illustration I shall describe only certain forms of procedure which may be followed in connection therewith.

Patented Sept. 22, 1936 PATENT omcs readies roe medicine r" SODIUM IWETAPH'Q S PHATE Charles S. Bryan,

Providence, R. I., assignor to Runlford Chemical Works, Rumford, R. L

no mating. Application,

Serial No. 753MB 6 Claims. (ch 23-107) My invention relates particularl'yto the purification of 'fntjaphos pfiats and espeeiany thetaphosphates of the alkali metals, seen, fo'rinstance, as ,ifioiiifitapliosphate 6f stidium or 156 any of their polymers, and product sulphuric acid This results in 6f the snium sent as nietaphosphate iii the subdent fusion.

remove such impurities.

usual process of the manufacture of exa'iiiple', enymetephostenses, for instance, phosit,ai5atite or bone material,

so as to term a hone acid, to which is'then sodium hydroxide, of

I sodium metaphosphate containing impiirities such as those mentioned above, is dis'- solvedin the proportion of 1 part by weight of aphosphate to 4 parts by weight of water. 'r water solution rthen add from 05 to .15 part preferably ll 0'%, by weight of sodium hydroxide' as comparedwith the metaphosphate, instead of which there may be added any other alkali inetal hydroxide or carbonate, to precipiweenie iion,aluminum,chromium and vanadium as the corresponding compounds, but not sufiicient sodium hydroxide, or alternative compound, as mentioned above; is added to re-dissolve the precip tated aluminum hydroxide as the latter is sfcgliibl in excess of sodium hydroxide. I now nee "off the precipitated compounds of iron, aluminum, etc, which are discarded and the filtrate is then evaporated to dryness, thus obtaining apurified sodium nietapho'sphate containing a slighfix'ti'ess or sodium hyaiexideae rding to thisto be advantageous in carrying out the procedure. There is thus obtained, on cooling, the metaphdsphate which has a slight alkaline reaction, althoughthe' slight excess of the sodium hydroxide just referrd to been decreased s inewnetas a result of the fusion, excess is almost completely neutralized thereby: There 'ill, or e6u1-s e ,e1se be more er the sodium metaphosphate obtained as a' result of this treatniiit; diving to the' fact that the iron and alumiare sie e-t there n as metaphosphates and frdr'ii the latter some sodium mtaphosphate will originally present in the orthophosphoric acid, but these impurities are practically completely removed in the subsequent precipitation with sodium hydroxide or the alternative alkali metal compound as given above.

th airs-1i metal compound added, as I have found 215 the said be formed by reaction with the sodium hydroxide This, of course, contains all of the impurities The product thus obtained, and which is the 55 sodium metaphosphate, has a slight alkalinity, but this does not interfere with the many industrial uses to which the metaphosphate is applied, as above referred to, but, in fact, is an advantage, not only because the alkalinity adds to the cleansing properties and is more satisfactory and economical for softening. water, but as, furthermore, thedry compound is more readily soluble in water by reason of the free alkali present.

While I have described my invention above in detail I wish it to be understood that many changes may be made therein without departing from the spirit of the same.

Also, wherever sodium metaphosphate. is referred to herein I mean to include thereby monosodium metaphosphate or anypolymer thereof.

I claim: 7

1. The process of purifying an alkali metal metaphosphate containing iron metaphosphate asan impurity which'comprises adding .05 to .15 part by weight of an alkali metal hydroxide or carbonate on the basis of one part by weight of the alkali metal metaphosphate, to a solution thereof to substantially eliminate all of the said impurity therefrom by precipitation and, then filtering off the precipitate. 2 The process of purifying sodium metaphos- 1" phate containing iron metaphosphate as an im-' purity which comprises adding .05 to .15 part by weight of an alkali metal hydroxide or carbonate on the basis of one part by weight of the sodium me'taph'osphate, toa solution thereof to substantially eliminate all of the said impurity by precipitation and then filtering off the precipitate. 3.' The process which comprises treating a phosphatic material withsulphuric acid, filtering to obtaina solution of orthophosphoric acid,,concentrating the same, adding an amount'of an alkali metal hydroxide or carbonate sufficient to form 'an'insoluble compound with an impurity therein but insufficient to cause the presence of an orthophosphate on fusion, thus obtaining an impure alkali metal orthophosphate, fusing to produce the alkali metal metaphosphate and purifying the alkali metal metaphosphate containing iron and aluminum metaphosphates as an impurity by adding .05 to .15 part by weight of an alkali metal hydroxide or carbonate on the basis of one part by weight of the alkali metal metaphosphate, to a solution thereof to substantially' eliminate all of the said impurity therephosphate on fusion, thus obtaining an impure sodium orthophosphate, fusing to produce the sodium metaphosphate and purifying the sodium metaphosphate containing iron and aluminum metaphosphates asan impurity by adding .05 to .15, part by weight of a sodium hydroxide or carbonate on the basis of one part by weight of the sodium metaphosphate, to a solution thereof to substantially eliminate all of the said impurity therefrom by precipitation and then filtering oif the precipitate.

5. The process which comprisestreating a phosphatic material with sulphuric acid, filtering to obtain a solution of orthophosphoric acid, concentrating the same, adding an amount of an alkali metal hydroxide or carbonate sufficient to form an insoluble compound with an impurity therein but insufficient to cause the presence of an orthophosphate on fusion, thus obtaining an impure alkali metal orthophosphate, fusing to produce the alkali metal metaphosphate and purifying the alkali metal metaphosphate containing iron and aluminum metaphosphates as an impurity by adding .05 to .15 part by weight of an alkali metal hydroxide or carbonate on the basis of one part by weight of the alkali metal metaphosphate, to a solution thereof to substantially eliminate all of the said impurity therefrom by precipitation and then filtering off the precipitate.

6. The process of purifying an alkali metal metaphosphate containing iron, aluminum, chromium and vanadium metaphosphates as an impurity which comprises adding .05 to .15 part by weight of an alkali metal hydroxide or carbonate on the basis of one part by weight of the alkali metal metaphosphate, to a solution thereof to precipitate substantially all of the said impurity, the samebeing added in a slight excess over the amount required to eliminate the impurity, and then filtering off the precipitate. 

